<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Favorites</title>
  <style>
    #popup{
      background-color: cornflowerblue;
    }
  </style>
  <script src="./src/background.js"></script>
</head>
<body>
  <div id="popup">
    background - html 
  </div>
</body>
</html>